Electric heater



Oct. 20, 1931. c. c, ABBOTT 1,828,635

ELECTRI C HEATER Filed April 29, 1929 Inventor: Charles C. AbbOt't,

His Attorney.

Patented Oct. 20, 1931 UNITED STATES PATENT. oF lcE cannon. orrrrrsrman, msa cnusn'rrs, ASSIGNOB r GENERAL ELEG- 'rmc comm, aconrona'rron or mew Yoax ELEGI'BIC imam Application filed April as,1929. Serial llo. averse.

My invention relates to electric heaters and has for its object theprovision of a simple,

eflicient and inexpensive electric heater and method of making it.

L Although it obviously has other applications, my invention isparticularly use connection with electric heaters provided forrelatively low temperature work. More specifically, my invention isparticularly useful in connection with electric. heaters employed toheat the lubricating oil of refrigerator apparatus.

In carrying my invention into effect in one form thereof, I provide aheating unit which comprises a supporting member upon which theresistance conductor is wound. Preferably, the supporting member will beformed from a suitable heat resistant material, such as asbestos. Eachend of the resistance unit will be secured to a suitable lead by meansof a terminal member which will be compressed, as by a swagin operation,about a portion of the turns of t e coiled resistance conductor and theend ortion of the lead. An electrically insulating sheath is provided tohouse the heating unit. Preferably, the sheath will be provided with apassageway shaped so that the heating unit when positioned within thesheath will have a substantially hairpin shape. Thus, in the finishedelectric heater,

. the heating unit carrym the terminals are adjacent each other.Odiviously, however, the heater may be formed in any suitable as shape.Thus, the sheath may be substantially straight with the leads projectingfrom the opposite ends.

For a more complete understanding of my invention, reference should behad to the 40 accompanying drawings in which Fig. 1 is an elevationpartly in section of an electric heater embodying my invention, and Fig.2 is a part sectional view illustrating themanner in which one end ofthe resistance conductor is connected to its lead, the view beingktakento a larger scale than Fig. 1.

eferring to the drawings, I have shown my invention in connection withan electric heater comprising a heating unit 10 which is provided withan electrically insulating v ulin the end portions of sheath or housing11 and a pair of leads 12. It will be understood that m service theseleads will serve to connect the heating unit with a suitable source ofelectrical supply, (not shown).

As shown, the heating unit 10 comprises an electrical resistanceconductor or wire 14, which will be wound or coiled upon a suitablesupporting member or core 15. Preferably, this supporting member will bemadeof a so suitable heat insulating, flexible and slightly yieldingmaterial such as asbestos. A flexible and yielding asbestos cord may beused conveniently for the supporting member.

Thus, the resistance conductor may be wound 66 continuously upon arelatively long length of the asbestos cord, after which the cord withthe conductor wound thereon may be cut into portions of the requiredlengths for the heatmg units.

The provision of the heat resistant, flexible supporting member 15 is animportant feature of my invention. It will be appreciated that in anelectric heater adapted for low temgerature work, it is desirable to usea very 76 neresistance conductor in order to secure the requiredresistance. In order to use satisfaetorily a very fine resistanceconductor, I." have provided the conductor with a heat resistantcorewhich serves both to support so the turns of'the resistance conductorand to retain the various turns in their proper spaced relation. It willbe observed that since the conductor is provided with a support which isslightly yielding, the conductor as it is 35 being wound will slightlydepress the outer surface of the support so that each turn of I theconductor will form its own recess. By reason of this construction anydisplacement of the'turns is prevented. It will e understood,however,,that the asbestos supporting member'15 is sufiiciently hard toprovide a com aratively stron and firm support for the 'ght conductor,1t being yielding mere- 1y to the extent of ermitting the resistance 96conductor to slight depress its outersurface. In other wor s, the, suporting member 15 will be one possessing su stantlal mechanical strength.

Each end of the heating unit will be suit- 100 till 2 saaose ablyconnected with its lead member 12. In order to secure the end portion ofthe resistance conductor to its lead 12 in good mechanical andelectrical relation therewith, 1 provide suitable terminal members 16.As shown (Fig. 2), each terminal member 16 is tubular in form and isprovided with a stepped bore, one portion 16a of which will serve toreceive the end or" the supporting member upon which the resistanceconductor is coiled while the other portions 166 and 160 of which willserve to receive the terminal end of the cooperating lead 12.

in assembling the terminal, it will be understood that the end of thesupport 15 will be inserted in the larger bore 16a of the terminal 16.The second step in assembling the terminal is to slightly compress orcrimp the receiving or inner edge of the terminal. 'lhis insures thatthe terminal will be held in proper position with respect to the coiledresistance conductor during the subsequent swaging operation. Then theend portion of the lead 12'which, of course, will have been bared of itsinsulation 12a will be inserted in the smaller portions 16?) and 160 ofthe here. The terminal member 16 will then be subjected to a swaging orlike process whereby its diameter will be reduced to such an extent thatthe terminal will be compressed into firm mechanical and good electricalcontact with the end turns of the coiled resist ance unit and the baredend portion or the lead 12. it will be observed, by reference to Fig. 2,that the terminal will be compressed about the end turns of the coiledconductor so that they will be depressed into the yielding surface ofthe asbestos support. As a matter of fact, it is preferable that thediameter of the asbestos supporting member itself be slightly reduced bythe compressed terminal. It also will be observed that the smallestportion 160 of the bore will be compressed tightly about the bared leadwhile the end of the lead will be received in the slightly largerportion 16b of the bore, Thus, the extreme end portion of the lead willform a head which together with the compressed portion 160 of theterminal will practically prevent thelead from being pulled out. It willbe understood that if it is desired, the terminal member 16 may beswaged to such an extent that its outer diameter will be substantiallythat of the outside diameter hi the coiled conductor. Preferably, and asshown, the resistance end of the terminal will be rounded or hellmouthed so as to prevent injury to the resistance conductor during theswaging operation.

After both oi the leads have been connected to the resistance conductorin the manner just described, the conductor is bent or otherwise shapedin the form or a hairpin so that in the finished heating unit the (Fig.1).

As has been pointed out, the heating unit will be provided with asuitable electrically insulating sheath or housing l1. Preferably, thissheath will be made of a suitable ceramic compound such as porcelain. Inorder to adapt the porcelain sheath for a ready assembly with thehairpin shaped heating unit, 1 provide the porcelain sheath with apair'of substantially parallelspaced passageways 11a and 11b, and on oneend with a recess 110 into which the passageways open. As shown, thepassageways extend from this recess longitudinally through the sheath toits opposite end where they open to the ex- Ierior of the sheath. Inassembling the heating unit with the sheath, the heating unit will bedrawn through the passageways 11a and lib, respectively, so that the legportions a and 10?) will be received in the parallel passageways whilethe bent or U-shaped portion of the heating unit will be received intherecess llc. it will be observed that in the assembled heater theleads '12 will be projected from the open ends of the passageways.Preferably, before the heating unit is positioned within the sheath, itwill be dipped in a suitable liquid cement such as liquid porcelaincement. It will be understood that the entire heating unit including theterminal portions will be dipped in the liquid cement. T his cement whenhardened serves to anchor the windings and terminals within the sheath.Thus, in the event the asbestos support becomes charred or weakened byreason of excessively high temperatures, the turns of the woundconductor and likewise the terminals will be held in place.

After the heating unit has been assembled with its sheath 11, the recess110 will be completely filled with a suitable liquid cement, such'asliquid porcelain cementi After the recess has thus been filled, theheater will be placed into an oven and heated to a suitable temperatureand for a suitable length of time so that the entire sheath casing willbe dried until it becomes a hard porcelain mass.

It will be observed that I have formed an electric heater which not onlywill be mechanically strong and durable, but also will be of acomparatively inexpensive construction. The fine resistance conductor isrigidly supported upon the comparatively rigid core member while theleads 12 will be efi'ectively secured both mechanically and electricallywith the resistance conductor. The asbestos support 15 will withstandrelatively high temperatures without danger of'deterioration ordestruction.

It is to be noted that while I have described my invention specificallywith reference to a heating unit adapted to low temperature work, theinvention is equally useful in connection with high temperature heatingunits.

terminals are adjacent each other What I claim as new and desire tosecure by Letters Patent of the United States is: Y 1. A heating unitcomprising a supporting member, a resistance conductor wound upon saidsupporting member and a terminal member compressed about a portion ofsaidsupportingmember in contact with the conductor turns wound upon saidportion.

2. A heating unit comprising a yielding supporting member, a resistanceconductor wound upon said supporting member anda terminal membercompressed about said yielding supporting member so as to be inelectrical contact w1th a ortion of the turns of said coiled conductor.

3. A heating unit comprising a heat resistant supporting member,a'resistance conductor wound upon said supporting member, a lead forsaid resistance conductor and an electrical conducting member compressedabout a portion of the turns of said wound conductor and about a portionof said lead whereby said lead is secured to said resistance conductor.

4. An electrical heater comprising a heating unit having a yieldingsupporting memher, a resistance conductor colled about said tion of saidlead:

supporting'membema lead for said resistance conductor and means forelectrically connecting said resistance conductor and said leadcomprising a tubular member compressed about a portion of the turns ofsaid coiled-resistance conductor and an end porcontact with an endportionof said coiled resistance conductor, said tubular terminal memberbeing compressed about the. adjacent end of said lea whereby the-lead issecured to said resistance conductor.

- ance conductor wound upon sa1 7. A heating unit comprising asubstantially cylindrical asbestos sup ort, a resistsupportsubstantially to one end thereof, a lead for said resistance conductorpositioned with one end adjacent said end of the cylindrical support anda tubular terminal member for electrically connecting said lead to saidresistance conductor compressed upon the adjacent ends of saidcylindrical support andsaid lead.

8, An electrical heating unit comprising a substantially cylindrical,yielding support, a

resistance conductor wound upon said su port Substantially throughoutits length, a lead for each end of said coiled resistance conductor,each lead having one'end'positioned in substantial alignment with the associated end of the cylindrical support, and a tubular terminal for eachend of said resistance conductor whereby said end is mechanically andelectrically connected with the adjacent end of its associated lead,saidterminal havin a stepped bore, one portion of said bore icingcompressed about said end of the cylindrical support, while anotherportion of said bore is compressed about a portioniof said lead wherebythe adjacent end of said lead isprovided with a head for preventing thewithdrawal of said lead.

9. An electrical heater comprising an electrically insulating sheathhaving an o" n end, a supporting member mounted wit in said sheath, aresistance conductor mounted upon said supporting member, a leadprojecting into said sheath through its open end and a terminal mountedwithin said sheath for electrically connectin said resistance con-'ductor with said lea said terminal being compressed about said supportinso as to be in electrical contact w1th a portion of said electrical,conductor.

10. A. heating unit com rising an electrically insulating sheath liavingan open end, a yielding supporting member mounted within said sheath, aresistance conductor wound upon said supporting member and a terminalmountedwithin said sheath, said terminal being compressed about saidyielding supporting member so as to be in electrical contact withaportion of said electrical l conductor. a 11. A heatingunit comprisingan electrically insulating sheath having an open end. a yieldingsupporting member mounted within said sheath, a resistance conductorco1led ,abou t said supporting member, a lead for said resistanceconductor projecting from necting said resistance conductor an said leadcomprising a tubular member mounted within said sheath -and compressedabout a portion of the end turns of said coiled resistance conductor andthe end portion of said lead.

12. An electrical heater comprising a pormember said open end and meansfor electricall concelain sheath having a passageway shaped in I I I theform of a hairpin, the ends of said passageway being open to theexterior of'the sheath, an asbestos supporting member mounted withinsaid sheath so as to assume a substantially hairpin shape, a resistanceconductor coiled about said supporting member, substantially throughoutits length, a lead for each end of'said'coiled resistance conductor,said leads being projected into the open end portions of said passagewayso as to be in substantial alignment withthe corlar terminal membermounted within each leg 7 of said passageway so as to receive theassociated adjacent ends of said support and said leads, each terminalmember being compressed about said adjacent ends so as to provide a firmmechanical and good electrical connection between the end turns of saidresistance conductor and its leads.

13. The method of forming a heating unit which comprises winding aresistance conductor upon a yielding supporting member and then securingsaid resistance conductor to a lead by compressing a tubular terminalmember about a portion of the resistance conductor and'a portion of saidlead.

14:. The method of forming a heating unit which comprises coiling aresistance conductor upoma substantially cylindrical supporting member,then connecting a terminal member to the end of said coiled resistanceunit and a lead by placing the adjacent ends of the supporting memberand lead in a passageway formed in said terminal member whereby theterminal embraces the end turns of said coiled conductor and the end portion of said lead and then swaging said terminal into firm mechanicaland good electricalcontact with said resistance conductor and said lead.

15. The method of forming a heating unit which comprises winding aresistance conductor upon a yielding supporting member, then securingsaid resistance conductor to a lead by compressing a tubular terminalmember about a portion of the resistance conductor and a portion of saidlead and then surrounding said supporting member, resistance conductorand terminals with an electrically insulating covering.

16. The method of forming a heating unit which comprises coiling aresistance conductor upon a substantially cylindrical supporting member,then connecting a terminal member to the end of said coiled resistanceunit and to a lead by placing the adjacent ends of the supporting memberand lead in a passageway formed in said terminal member whereby theterminal embraces the end turns of said coiled conductor and the endportion of said lead, then swaging said terminal into ,Way of hairpinform is provided in said sheath for said heating unit.

In witness whereof, I have hereunto set my hand this 25th day of April,1929.

CHARLES C. ABBOTT.

firm mechanical and good electrical contact with said resistanceconductor and said lead, and then placing said support together with thecoiled resistance conductor and its terminals into an electricallyinsulating porcelain sheath.

17. The method of forming an electrical heater which comprises providina heating unit by winding a resistance con uctor upon a flexiblesupporting member, then shaping said heating unit to the form of ahairpin, then drawing the legs of said heating unit into an electricallyinsulating sheath having a recess in one end and a pair 'of spaced

